Free piston motor compressor



July 6, 1937. H. JNxcKE I 2,086,228

' FREE PIs'roN Mforz coMPREssoR I Filed Feb.- 23;'1935 a sheets-'sheet 1v orma@ July 6, '1937.

H. JANICKE FREE PISTON MOTOR COMPARESSOR Filed Feb. 25K: 1955 3 rSheets-"Sheet 2v H. JNICKE FREE PISTON MOTOR COMPRESSOR' July s, 1937.

3 Sheets-Sheet 3 Fig. 3

/n ventor al Patented July 6, 1937 UNITED STATES PATENT OFFICE FREEPISTON MOTOR. COMPRESSOR Hermann Jnicke, Dessau, Germany, as signor toTherese Junkers, Gauting, near Munich, Gerlllaflly 20 Claims.

My invention relates to free piston motor compressors. It is an objectof my invention to provide means whereby the output'of compressors ofthe kind aforesaid can be controlled in a particularly simple andefficient manner.

In my copending- U. S. application Serial No. 710,483 I have discloseda'method of controlling a free piston motor compressor by varying thelength of stroke and the pressures thereof, e. g. the suction ordischarge pressure, or a combination of both these pressures. Mycopcnding U. S. application Serial No. 7,786 discloses the control of afree piston motor compressor by means of a variation of the dead spaceand the fuel supply in a manner such that the piston stroke alwaysremains approximately constant, independently from the variation of thecompressor output, While my copending U. S. application Serial No.7,788. discloses the regulation of a free ypiston motor compressor bythe simultaneous variation of at least two of the variables, which at apredetermined constant stroke of the piston determine the output of thecompressor as well as the return energy in such a manner that theportion 25 of the total return energy available for the compression ofthe motor charge must always remain 'approximately constant.

In free piston motor compressors comprising a combustion chamber and oneor more compressor chambers, and one or a plurality of freelyreciprocating pistons, it has already been suggested to vary theperformance of the compressor by varying the length of stroke of thefree pistons. Such variation of 4stroke involves certain drawbacks, asthereby the-control of the motor part of the machine, which' is derivedfrom the movement of the free pistons, is subjected to undesirablevariations.

It is an object of my invention to enable the performance of thecompressor to be varied within Wide limits at substantially constantstroke.

This is eected according to the present invention by regulating theperformance of the compressor by varying the pressures and, at the sametime, influencing the supply of fuel to the combustion chamber of themotor in such manfree pistons remains (b) The suction pressure; the jperfxirmancek drops if 4this pressure is lowered, and vice versa; (c)The delivery and suction' pressures may be varied at the same time; theymay be varied in opposite senses, in which case the influences ex` ertedon the performance by suchvariations of pressure add. Alternatively theymay be varied v in the same sense, in which .case the performance variesin conformity with the difference between the influences 0I thepressure` variations. In the case last mentioned the proportion of 'thetwo pressures may be constant and, if the initial temperature isconstant, the inaltemperature of thel compressed gas will also remainconstant.

In some cases the problem is to vary the amount of energy taken up or ofenergy delivered, by additional chambers such as, for instance,pneumatic buffers which store compression energy during one stroke anddeliver it during the subsequent stroke, this delivered energy, togetherwith the energy which is released in the compressor proper upon thereturn stroke, compressing the charge in the combustion chamber. Insuch" additional chambers the same procedure may be adoptedas in thecompressor chambers proper, i. e. a variation of pressures, such as, forinstance. the initial pressure of compression, at substantially constantstr ke of the free piston or pistons.

The controls to be effected. according to this invention, i. e., thevariation of pressures and the variation of the quantity of fuelsupplied to the motor per power stroke,4 mayY be' effected eithermanually orautomatically, or one of them manually, the otherautomatically. y l

Manual control is adoptd, for instance;r if there arise comparativelyfew v or slow variationsof the demand for compressed` gas',' "or "`if"the frequire ments as tothe exactitudel of controllare vnot high. Withsuch a control the variations of pressure as well as the variation ofthefuel'supply may be derived from the same control member (a hand Wheel, alever, or the like) so that each 40 control operation requires only theactuation of this one member. f

If both controls are effected automatically, they' may be inuenced bythe variations of a single source of power,'for instance,4by thepressure in a storage tank arranged in series with the compressor. Inthat ease both control operations are connected in parallel and aresuitably tuned with respect to each other. j

However, it is also possible, to render one control'operation dependentof the other, for instance by regulating the pressure inthe compressorin dependency upon the pressure in a storage tank, while the supply offuel is regulated in dependency upon the pressure in the operationsdependent from distinct conditionsl which are not directly related toone another, for instance, to again vary the pressure in the compressorin dependency upon the pressure in the storage tank, but to regulate thesupply of fuel to the motor part in dependency upon the stroke in suchmanner that this stroke remains substantially constant.

I will now proceed to describe my invention with reference to thedrawings affixed to this specification and forming part thereof, inwhich several embodiments of this invention are illustrateddiagrammatically by way of example.

In the drawings Figs. 1, '2, 6 and 8 are axial sections of free pistonmotor compressors with oppositely reciprocable pistons, each of the lasttwo figures show;- ing one-half of the machine while Figs. 3, 4 and 5are diagrams showing pressures plotted against stroke for thecompressors illustrated in Figs. 1 and 2, and

Fig. 'lis a similar diagram for the pneumatic buffer illustrated in Fig.6.

In the free piston motor compressors shown in Figs. 1, 2, 6 and 8, l isthe casing of the motor andv 2 is the central combustion chamber with acompressor chamber 3 at each end. Ihe free pistons are formed by enginepistons 4 and compressor pistons which are directly connected. In orderto warrant absolute synchronism of the opposite reciprocatory movementsof the pistons, they are connected 4by suitable mechanism, for instancea rack I5 connected to each piston, the racks meshing at diametricallyopposite points with a pinion IB which is Ymounted for rotation in afixed position on the casing I. The left hand motor piston controls thescavenging ports 6 and the right hand motor piston controls the exhaustports 'l inthe wall of the motor cylinder. 'I'he residual compressed gaswhichrernains over in the dead spaces of the compressor at the end ofevery power Vstroke expands and forces the free pistons toward eachother. When the pressure in 'the compressor cylinders has dropped tosuction pressure, fresh gas is drawn in through the suction valves 8and, at the same time, the charge in the combustion chamber 2 iscompressed. Toward the end of the: return str ke liquid fuel is injectedinto the combustion ch mber 2 through pipe 22 and injection nozzl 23 bymeans of a fuel pump having a piston 20rand a cylinder 2I, and themixture is ignited. ,'The fuel pump, which is more fully described in mycopending application Serial No. 710,483, is operated by a cam 24 formedon the rack I5, which, when the piston is near the end of its inwardstroke, turns a rocker 25 which displaces the pump piston 20 against aspring 26.. The products of combustion in the combustion chamber forcethe pistons apart, the gas which has been drawn into the compressorcylinders, is compressed and conducted to a. storage tank I3 throughdelivery valves 9, delivery pipes I9 and delivery main. II. A pipe I4distributes the compressed .gas to the individual stations where it 1srequired. `Aspring-loaded check valve I2 is provided in the main II forholding the compression pressure in the compressor chambers at apredetermined minimum even if the pressure in the reservoir should belower than the minimum, for instance in consequence of heavy tappings ofcompressed gas, or when the compres-sor .is

started. 'I'he check valve I2 may consist simply-me. g. in a mannersimilar to that shown in Fig. l-ofa valve body 4I, 42, which a spring 40tends to close. The top of this spring abuts against a spring abutment44, which, however, in contradistinction to the showing of Fig. 1, cannot be varied as to its position, but may be pro- ',vided either as thecover of the valve casing itself or as some other part rigidly connectedwith said casing. In this case the'force of the spring acting upon thevalve body is always maintained constant. Since the delivery pressure inthe compressor `is solely determined by the force of the spring, thedelivery pressure in. the compressor likewise can always be maintainedat a predetermined minimum value, i. e. may be constant, as indicated inFig. 4 of the application, 'according-to which the suction pressure onlyisf varied, while the delivery pressure, despite the aforesaidvariation, has remained constant. On the other hand the check-valve I2can be arranged for 'a variable force of the spring 40 in such a mannerthat the delivery pressure of the compressor also is rendered variable.A valve of this kind is described below in greaterdet l with referenceto Fig. 1.

' e amount of fuel supplied'to the motor per power stroke is regulatedautomatically in dependency upon the pressure in the storage tank ,oneface of the piston, while the pressure in the tank I3 acts on the otherface. 'I'he position of the piston 32 is thus determined by the pressurein the tank I3, and consequently the amount of' fuel delivered at eachstroke of the pump is a function of this pressure'.

Figs. 1 and 2 further illustrate means for regulating the compressorperformance by a variation of pressures.

As shown in Fig. v1, a valve loaded by a spring 40 and opening towardthe storage tank is inserted in the main I I leading to the storagetank. The spindle 4I of the valve has the size of a piston so that thevalve seat 42 is relieved of the pressure in the tank, and the deliverypressure of the compressor is determined by the tension of spring 40exclusively. This spring tension, in the example illustrated, isregulated automatically in dependency upon the pressure in the tank. Tothis end a wedge member 45 is inserted between the end wall 43 of thevalve casing and the spring plate 44 acting like a piston.

The wedge member .is connected to a piston 49 valve spring 40 isincreased, the delivery pressure of the compressor rises in proportionand the performance is reduced. Obviously the increase of pressure inthe compressor can be much greater than the increase of pressure in thetank I3, and the regulation will therefore be rapid and powerful. A

If it is desired to manuallyregulate the compression pressure, the wedge45 and the means' for Shifting it are replaced by a threaded spindlewhich is inserted in the end wall 43 of the valve casing and exertspressure on the spring plate 44.

Fig. 2 shows means for regulating the performance of the compressor byvarying the suction pressure. Here all the suction valves 8 areconnected to a suction pipe I in which a throttle valve 50 is mountedto' slide, which is connected to a piston 53 which, through a pipe 54,is acted upon by the pressure in the tankV I3 in such manner that thispressure tends to close the throttle valve, While a spring 55counteracts the pressure on the piston. The spring is so designed thatthe throttle valve is closed in proportion as the pressure in the tankI3 rises beyond the normal, and the suction pressure is progressivelyreduced.

The control of the supply of fuel to the motor may be effected independency upon the pressure in thetank, as shown in Fig. .1.

The fuel supply may, however, also be regulated in dependency upon thesuction pressure, as shown byway of example in Fig. 2. To this end thepipe 35 leading to the cylinder 33 of the fuel-regulating device,instead of being connected to the tank I3, is connected to thecompressor chamber 3,this connection ending at 59 in the vicinity of theend face of the compressor piston 5 when this piston has just startedfor the compression stroke. Mountedv in the pipe 35 is a closing memberhaving the form of a slide valve 60 formed with a port 6I. This slide isconnected to the short arm of a rocker 62, the long arm of which isengaged by a pin 63 on the rack I5, so that the reciprocatory movementof the pistons is transmitted to the slide 6I). The ar-- rangement issuch that the port 6I connects the compression chamber 3 to the cylinder33 only if suction pressure acts on the opening 59, the connection beingsevered when the compressor piston the pressure at the rear of thecompressor piston .Cil

5. In this manner interference of this pressure with the operation ofthe fuel-regulating device 30-34 is prevented.

Fig. 3 is a diagram illustrating the Way in which the compressor iscontrolled by an increase of the delivery pressure. A B C D A is thediagram for the normal operation of the compressor.' Compression occursfrom the suction pressure p1 tothe delivery pressure pz. If the deliverypressure is raised to p21, the new compressor diagram is 'A Bz C2 D1 A.The suction line D1 A of this new diagram is shorter than the suctionline D A of the normal diagram. The quantities of gas drawn in, andconsequently also the quantities of gas delivered, vary in the sameproportion as these lines.

Fig. 4 is a diagram showing the control by a reduction o f the suctionpressure.

the new diagram is A2 Bi C Dz A2.` The performances are proportionedsimilarly as the line B C (at normal performance) relative to the lineB1 C (at reduced suction pressure).

Fig. 5 is the diagram of a compressor in-which i" the performance isregulated by simultaneously varying the delivery and suction pressuresin opposite senses. If the performance of the compressor (the normaldiagram of which is again A B C D A), shall be reduced, the suctionpressure is reduced from p1 to p11, While the` delivery pressure isincreased from p2 top-2i. The new diagram is Az B2 C2 D2 A2. Theperformance is Here again A B C D A is the diagram of normal-operation.If the suction pressure is reduced from p1 to p11,

reduced in the proportion of the products from suction line and suctionpressure.

Fig. 6 shows a free piston motor compressor with a pneumatic buffercomprising a cylinder 65 and a piston 66 which absorbs energy during thepower stroke of the freelymoving masses, stores this energy in its deadspace under the form of compressed gas, and returns it to the freelymoving masses A during their return stroke. The amount ofl energyabsorbed and delivered by the buffer is regulated, according to thisinvention, by varying the pressure existing in the buffer space at thebeginning of compression.l To this vend the space 61 is connected tothestorage tank tank I3 rises to the higher value pn, the new compressionline is U V, and the energy absorbed and delivered by the buffer israised by an amount corresponding to the area S T V U S.

The buffer, or an additional'compressor or the like,.may also be soarranged that it absorbs' energy upon the return stroke of the freelymoving mas's, and delivers such energy upon the power stroke of thesame. If the compressor piston is larger than the motor piston, thedifferential piston area of the two, andthe .space 'I0 (Fig. 1) in whichthis differential area operates, may constitute the buffer or additionalcompressor.v The amount of energy absorbed by such buffers or compressorchambers during the return stroke of.

the freely movable masses may also be varied by pressure variation, asillustrated, for instance, in

Fig. 8. The space 'I0 adjoining 'the left hand side of the compressorpiston 5 may, for example, be a scavenging pump equipped with suctionvalves 1I and delivery valves 12. the delivery valves 12 to thescavenging air tank 'M (Fig. 6). A throttle 15 is insertedin this pipewhich, in a manner similar to the throttle according to Fig. 2, isinfluenced vby the pressure in the tank I3 in such manner that itsthrottling action is increased when ,the pressure rises, and vice versa.f r

I wish it to be understood that I do not desire to be limited to theexact details of construction shown and described for obviousmodifications will occur to a person skilled in the art.

1. A free 'piston motor compressor comprising in combination, a'motorcylinder and at least one compressor cylinder arranged o-n either s idethereof, a fre'e piston in each cylinder, comprising a motor piston anda compressor piston arranged on the same' side of the motor cylinderbeing directly connected with each other, means for varying one of theinitial and en d pressures in said compressor cylinders and means for atthe same time varying the supply of fuel to sai-d motor cylinder in suchmanner that the length of the piston stroke remains substantiallyconstant.

2. A free piston motor compressor comprising in combination, a motorcylinder and at least one `compressor cylinder arranged on either sidethereof, a free piston in each cylinder, comprising a motor piston and acompressor piston arrangedr on the same side of the motor cylinder beingdirectly connected with each other, means for vary- A pipe I3 extendsfrom inder, a free piston in each of said cylinders, comprising a motorpiston and a compressor piston arranged on the same side of themotorcylinder' being directly connected with each other, means forvarying one of the initial and end pressures in said compressor andadditional compression cylinders, and means for at the same time varyingthe supply of fuel to said motor cylinder in such mannerv that thelength of the piston stroke I .f'emains substantially constant.

4. A free piston motor compressor comprising in combination, a motorcylinder, at least one compressor cylinder arranged 'on either sidethereof and at least one additiogal compression cylinder, a free pistonin each o f said cylinders, comprising a motor piston and a compressorpiston arranged on the same side of t e motor cylinder being directlyconnected wi` h each other, means for varying both the initial and` endpressures in said compressor and additional compression cylinders, 'andmeans for ait the same time varying the supply of fuelt vsaid motorcylinder in such manner that the ength of the piston stroke remainssubstantially constant.

-5. A free piston motor compres'oiL comprising in combination, a motorcylinder, a pluralityof compressor cylinders arranged on either sidethereof, a free piston in each of said cylinders, comprising amotorpiston and a compressor piston arranged, on the same side of the motorcylinder being directly connected with each other, means for varying oneof the initial and Aend pressures in part of said compressor cylindersand means for at the same time varying the sup- .ply of fuel to saidmotor cylinder in such manner that the length of the piston strokeremains substantially constant. Q

6. A free piston motor compressor comprising in combination, a motorcylinder, a plurality of compressor cylinders arranged on either sidethereof, a free piston in each of said cylinders, comprising a motorpiston and a compressor pist0n arranged on the same side of the motorcylinder being directly connected with eachother, means for varying boththe initial and end pressures ln part of said compressor cylinders andmeans for at the same time varying the supply of fuel to said motorcylinder` in such manner that the length of the piston stroke remainssubstantially constant.

7. A free piston motor compressor comprising in combination, a motorcylinder, at least one compressor cylinder arranged on either sidethereof, and at least one pneumatic builer cylinder, a free piston'v ineach cylinder, comprising a vmotor piston and a compressor .piston`arranged compressor cylinder arranged on either side thereof, and atleast one scavenging pump cylinder, a free piston in each-cylinder,comprising a motor pistonand-a compressor piston arranged on the sameside of the motor cylinder being directly connected with each other,means for varying one of the initial and end pressures in saidcompressor cylinders and in said scavenging pump cylinder, and means forat the same time varying the supply of fuel to said motor cylinder insuch manner that the length of the piston stroke remains substantiallyconstant.

9. The combination, with the free piston motor compressor of claim 2, ofmeans for keeping the relation between the initial and the end pressuresin said compressor cylinders constant.

10. The combination, with the free piston motor compressor of claim 4,of means for keeping the relation between the initial and the endpressures in said compressor cylinders constant.

11. The combination, with the free piston motor compressor of claim 1,of means for regulating the fuel supply to the motor cylinder. in

dependency from one-of the initial and end pressures, subjected tovariation, in the compressor cylinders.

12. A free piston motor compressor comprising in combination, a motorcylinder and at least one compressor cylinder arranged on either sidethereof, a free piston in each cylinder, compris- 3 ing a motor pistonand a compressor piston arranged on the same side of the motor cylinderbeing directly connected with each \other, means f' sametime varying thesupply of fuel t said supply.

motor cylinder in such manner that the length4 of the piston strokeremains substantially constant, and Va. single adjusting member adaptedto effect the. variation of one of said pressures and of saidfuelsupply.

13. A free piston motor compressor comprising in combination, a motorcylinder and at least one compressor cylinder arranged on either sidevarying both the initial and end pressures in` said compressorcylinders, means for at the same time varying the supply of fuel to saidmotor cylinder in such manner that the length of the piston strokeremains substantially constant, and a single adjusting member adapted toeffect the Avariation bothv of said 14. A free piston motor compressorcomprising in combination, a motor cylinder and at least one compressorcylinder arranged on either side thereof, a free piston in eachcylinder, comprising a motorl piston and a compressor piston aron 'thesame side of the motor cylinder being directly connected with eachother, means for varying one of the initial and end pressures in saidcompressor cylinders and in said pneumatic buffer cylinder, and meansfor at the same time varying the supply of fuel to said motor cylinder-`v-in such manner that the length of the piston ranged on the same sideof the motor cylinder being directly connected with each other, meansfor varying one of vthe initial and-end'pressures in said compressorcylinders, means for at the same time varying the supply of fuel to saidmo- 4tor cylinder in such manner that the length of the piston lstrokeremains substantially constant,

pressures and of said fuel A and a single source of power adapted tomove both said members.

15. A free piston motor compressor comprising in combination, a motorcylinder and at least one compressor cylinder arranged on either sidethereof, a free piston in each cylinder, comprisin 'g a motor piston anda compressor piston arranged on the same side of the motor cylinderbeing directly connected with each other, means for varying both 'theinitial and end pressures in said-compressor cylinders, means for at thesame time varying the supply of fuel to said motor cylinder in suchmanner that the length of the piston stroke remains substantiallyconstant, and

, a single source of power adapted to move both cylinders, means forvarying the cross-sectional said members.

`16. A free piston motor compressor comprising in combination,- a motorcylinder and at least one compressor cylinder arranged on either sidethereof, a free piston in each cylinder, comprising a motor piston and acompressor piston arranged on the same side of the motor cylinder beingdirectly connected with each other, a compressed air conduit connectedto said compressor cylinders, a valve inserted in said conduit and sub-'jected to the discharge pressure of said compressor, a spring arrangedto counteract the discharge pressure acting on said valve, means forvarying the tension of said spring in dependency from'the f pressureprevailing in saidA conduit to the rear of said valve and means forvarying .the supply of fuel to said motor cylinder in such manner thatthe length of the piston ,stroke remains substantially constant.

17. A free piston motor compressor comprisingv in combination, a motorcylinder and at least one compressor cylinder arranged on either sidethereof, a free piston in each cylinder, comprising a motor piston and acompressor piston arranged on the same side of the motor cylinder beingdirectly connected with each other, suction valves on said compressorcylinders, a suction conduit communicating with said valves, a pressurecon.- duit for the gas compressed in said compressor area of passage of-said suction conduit in dependency from the pressure in said pressurecon- -duit and means for varying the supply of fuel to said motorcylinder in such manner that the length of the piston stroke remainssubstantially constant. 'Y

18. A free piston motor compressor comprising in combination, a motorcylinder, at least one compressor cylinder arranged on either sidethereof, and at least one pneumatic bu'er cylinder, a free piston ineach of said cylinders, comprising a motor piston and a compressorpiston arranged on the same side of the motor cylinder being directlyconnected .with each other, each buier cylinder being xed in alignmentwith the corresponding compressor cylinder, a pressure v conduit for thegas compressed in one compressor cylinder, said pressure conduit beingconnected` to'the corresponding buler cylinder near` the point at whichthe end face of said buier piston is located 'before compressionisstarted, and

means for varying the fuel supply to said motor cylinder in such mannerthat the length of the piston stroke remains substantially constant.

19. A free piston motor compressor comprising in combination, a motorcylinder, at least one compressor cylinder arranged on either sidethereof and an additional compression cylinder.' a free piston in eachof said cylinders, comprising a motor piston and a compressor pistonarranged on the same side of the motor cylinder being directly connectedwith each other,`means for varying one of the initial and end pressuresin said compressor cylinders, and means for at the same time varying thesupply of fuel to said mo- 4tor cylinder in such manner that the lengthof the piston stroke remains substantially constant.`

20. A free piston motor compressor comprising in combination, a motorcylinder, at least one compressor cylinder arranged von either sidethereof and an additional compression cylinder, a free piston in each ofsaid cylinders, comprising a motor piston and a compressorvlpistonarranged on the same sideof the motor cylinder bein-g varying boththe initial and end pressures in said compressor cylinders, Aand meansfor at thesame `time varying the supply of fuel to said motor cylinderin such manner that the length of the piston stroke remainssubstantially constant.

HERMANN JNICKE,

